Max Temp*

400°F

200°F

Motivation

Though the Jabiru engine is well designed, our research has found the following issues can occur when running heads at elevated temperatures:

Head distortion (creeping), due the Aluminium alloy yielding

Leaking heads, resulting in poor compression and loss of performance

Chronic head detonation

Valve recession

Cylinder stud failure, directly attributed to detonation

Head seating recession

Valve failure

Significantly reduced TBO

Solution

Previously, temperatures were combated by running excessively rich fuel mixtures to decrease head temperature, also leading to detonation. This wasn’t enough to alleviate the problem, and additionally increased fuel consumption. It was devised that increasing the cooling capacity of the engine eliminates all problems related to temperature. The most cost effective solution is to replace the entire head with a water cooled alternative.

Water Cooling vs. Air Cooling

Water has more than 20 times the thermal conductivity of air (ability to conduct heat).*

Water has over 4 times the specific heat of air (the amount of heat it takes to raise the temperature by 1°C).*

Opposed to removing heat from the surfaces of the head in a constricted cowl area, a water jacket, gives the ability to remove heat directly from the hottest part of the engine; the exhaust valve.

Due to cooler heads, yielding no longer occurs, and head bolts will not need to be re-torqued.

Testing and Final Product

The standard air cooled Jabiru 3300 engine will reach CHT limits within 2 minutes of high power static operation. The prototype LCH 3300 test engine, fitted with Rotec LCH ran for 4 hours continuously at WOT and the water temperature never exceeded 85°C (185°F). The CHT measured under the spark plug of the rear most cylinder peaked at 110°C (230°F). These tests were repeated over a period of 2 weeks of solid ground running and the results were the same every time. The ambient temperature during these tests peaked at 31°C (87.8°F). Needless to say the results not only met but exceeded our expectations. After around 30 hours of ground running it was decided to install the engine back into the SP6 Jabiru airframe where it came from and take it for a fly! See the third party testing in this testimonial.

Product Range

Product Range

Jabiru Liquid Cooled Head Kits

Jabiru 2200 4 Cyl LCH Kit

Jabiru 3300 6 Cyl LCH Kit

Jabiru 5100 8 Cyl LCH Kit

All Jabiru Liquid Cooled Head Kits by Rotec Aerosport come with all parts required to accommodate original Jabiru components. Only necessary replacement parts have been provided to keep the user price to a minimum. Liquid Cooled Heads come with new; valve guides, valve seats, head bolts and head bolt washers.

Water Temperature Kit

Start first time every time.

Simple ‘bolt on’ upgrade.

Never worry about your charging system again.

Simple ‘bolt on’ upgrade.

Water Temperature Probe

Water Temperature Gauge (in °C or °F)

5/8″ rubber pipes have a single bend, and are 1270mm long. 5/8″ pipes are to be cut by user to fit configuration. Off-cuts will be used to connect the 2 banks of cylinder outlets in series. Please refer to documentation for more details.

6 cylinder installations may use the 15L/min pump where cooling performance is exceptional. For example see Jim Wickam’s Spitfire with wing mounted radiator for reference. Fiberglass air ducts must be retained when using a 15L/min pump on 6 cylinder installations.

Pump kits come with all mounting accessories required. Electronic controllers are also available.

Radiator mount only available on SP6 engine cowl.

FAQ

Jabiru LCH General FAQs

Jabiru aircraft engines are popular among the sport aviation community. Rotec have recognized that the engine is well put together, although the lack of cylinder cooling is where most of the serious issues arise.

Careful operation of the air cooled Jabiru is required to avoid permanently damaging the cylinder heads or other parts of the engine. The Rotec LCH conversion eliminates technical issues relating to head temperatures, therefore greatly enhancing engine reliability.

Rotec press the valve seats into cylinder heads the same way Jabiru or any other head manufacture would. The press we use is the same we have been using on our radial engine heads since conception, and we have never had a valve seat fall out! A 0.15mm interference is used between the valve seat and the head.

Although inappropriate interference is not the culprit to why a head can be susceptible to having its valve seats fall out. The standard Jabiru air-cooled head simply get too hot and expand at a greater rate than the steel valve seat. The temperature high enough that interference between the seat and the head disappears and thus the seat falls out!

This can not happen with the liquid cooled heads as operating temperature are too low to get a significant differential expansion. Liquid cooled heads run at a similar temperature that a modern water cooled car engine, around 80 – 90 °C (180 – 200 °F).

The airframe with engine and Rotec LCH kit are sent to your location. The conversion is performed at your leisure, something many of our customers have done.

The airframe is sent to your location. The engine is sent to Rotec. Once the engine is converted, it is returned to you to install onto the airframe. This saves on shipping the airframe from Jabiru, to Rotec, to you.

Rotec purchase the airframe with engine and send to our facilities. The aircraft will be fully assembled (if necessary), converted and test flown. Once complete, the aircraft is sent to your location. With this option, significant discounts can be offered on other upgrades components.

Anyone who can install a standard Jabiru head can install a Liquid Cooled Head, as it is a similar installation process. It is not a difficult job. Liquid cooled heads are not certified and are an experimental product, so anyone is allowed to install them.

If desired, Rotec can fit new or used valves train components (i.e. valves, valve springs, spring retainers, valve collets, base washers and rocker arms), to LCH on behalf of customers. New components can be purchased through Jabiru Aircraft Pty. Ltd. Customers wishing to add valve train parts already in possession to their LCH order, can send them to our facilities.

Note: Hydraulic or solid lifter engines use different rocker arms. You must inform Rotec of you engine type to ensure the correct rocker arm is used. Click here to learn how to determine your engine type.

It is preferred that hydraulic lifter engines have their valve train components sent to our facilities for installation. Hydraulic lifters have approximately 4 mm of adjustment. This can make it difficult to have the correct seat depth without having valve to match them to.

The added weight of coolant, piping and radiator, is practically negligible. To date no installation has required any weight adjustments to balance the air frame, so minor changes to the center of gravity are negligible.

See weight comparison of a Jabiru 2200 head vs a Rotec LCH head for more information.

For information on Jabiru warranty, it is advised you contact Jabiru. Keep in mind receiving warranty from Jabiru is almost impossible anyway. Rotec are more interested in making your engine last and run at reliable temperatures, rather than worrying about warranty!

Jabiru LCH Technical FAQs

For later model hydraulic lifter engines, the external rocker oiler ports are bridged with rubber tube as no oil feed is present. Other than that, there are no difference between liquid cooled heads installed on a hydraulic and solid lifter engine.

All stock Jabiru components are transferred to the LCH head, i.e. rockers, valves, push rods, push rod tubes, spark plugs, as these are all retained and located in exactly the same location.

To identify whether an engine uses hydraulic or solid lifters:

Remove one rocker cover from any head

Observe the rocker arms inside

If there are valve adjusters on the rocker arm, the engine uses solid lifters

The absence of valve adjusters will indicate the engine uses hydraulic lifters

Note: Valve adjusters are used to adjusting valve clearances, traditionally consisting of a grub screw and a lock nut to maintain tension.

A Jabiru engine upgraded to Liquid Cooled Heads will run far better on automotive gasoline (Mogas) than an engine running standard air-cooled heads. The reduced cylinder head temperatures will greatly diminished the risk of detonation. Mogas is more susceptible to detonation than aviation gasoline (Avgas) due to its lesser octane rating and inferior purity.

We cannot recommend a coolant capacity for your installation as there is no standardized setup. The following values are capacities for the average installation including; a 200mm x 300mm radiator, pump, piping, head volume ect. The average installation has the radiator located about 1 meter from the rows of heads.

Jabiru 2200 ≈ 2.5 L (85 fl oz)

Jabiru 3300 ≈ 3.5 L (120 fl oz)

Jabiru 5100 ≈ 4.5 L (155 fl oz)

We recommend a coolant mix of 50% water and 50% antifreeze (ethyl glycol). This gives you a boiling temperature of 107 °C (225 °F). Increasing the percentage of antifreeze in your coolant mix will increase the boiling temperature, although it will degrade cooling performance in a short time. This is due to a build up of solids from the antifreeze on the walls of the cooling core. If higher boiling performance is required we recommend using a waterless coolant such as Evans NPG+ Waterless Coolant. Evans claim a boiling temperature of 190 °C (375 °F) allowing for maximum protection during high altitude flight.

Pumps are available with LCH purchases. For details contact us. See recommended radiator sizes here.

Note: Tests have shown that with the electric pump switched off, a Jabiru 3300 LCH conversion can fly at reduced power for approximately 45 minutes within safe temperatures.

Mechanical Fuel Pumps:

A mechanical water pump could be added and driven from the Jabiru engine accessory pad. However, it has been found that an electrical water pump is just as efficient and easier to install. A redundant pump can be installed if desired, although is in no way mandatory.

Without Integrated Filler Port – Radiator must be mounted below the coolant level. Coolant instead enters the system from a separate filler neck located at the top of the system. These are supplied as standard with LCH piping kits.

With Integrated Filler Port – Optional, for top mount radiators where a header tank is not used

Sourcing:

Radiator(s) are not supplied with LCH kits as all installation requirements vary. Use small motorcycle radiators, otherwise performance racing radiators can be fabricated relatively cheaply. You can even adapt a Rotax 912 cooling system.

Fiberglass air cooling ducts can be removed from LCH installation using appropriate liquid cooling. They’re no longer required as heat is now removed from the heads via coolant and dissipated through the radiator. They can be retained if desired despite being redundant.

It is entirely possible to integrate a cabin heating system into your aircraft. Adding a heater core, and extra piping into the cooling system circuit provides your with the bare essentials in creating a cabin heater.